In the decade since the start of combat operations in Afghanistan and Iraq, the military has relied increasingly on robots. Drones and bomb-removal bots have been designed to keep troops out of harm's way. Now the U.S. Department of Defense is looking for sleeker, faster robots that can assist with a wider range of missions.

The Cheetah, pictured at the right, is one of the new breeds under development. Real cheetahs, which can sprint up to about 120 kilometers per hour, are the fastest-running animals; the robot, made by Boston Dynamics in Waltham, Mass., reaches nearly 30 kilometers per hour, making it the fastest-legged robot.